i need some help with the /forceload command

hello to all minecraft lovers , i'm playing right now unmodded singleplayer survival and i stumbled upon a new command that was added in 1.13.1. this command is /forceload which can force a chunk to be loaded even if i'm far far away from home , which is great in my opinion and i don't consider that cheating , because that's how real life works right , your house doesn't get unloaded when you go to work and your pets need food when you're away , you get this point :)))) . my big questions are : How many chunks can I force load ? , Why when i forceload one chunk I can't force others because when i type " /forceload add <chunk coordinates>" i get that message "No chunks were marked for force loading" . thank you in advance!!!

So I think that you have to add two pairs of coordinates (x, z)(x1,z1) to select one chunk by choosing two blocks which are one with the lower x,z coordinates and the other with the bigger x,z coordinates. I can't test it right now.